class Solution {
    int dx[4] = {0, 0, 1, -1};
    int dy[4] = {1, -1, 0, 0};

public:
    int nearestExit(vector<vector<char>>& maze, vector<int>& e) {
        int m = maze.size(), n = maze[0].size();

        bool vis[m][n];
        memset(vis, false, sizeof vis);

        queue<pair<int, int>> q;
        q.push({e[0], e[1]});
        vis[e[0]][e[1]] = true;

        int step = 0;
        while(q.size())
        {
            step++;
            int sz = q.size();
            for(int i = 0; i < sz; i++)
            {
                auto [a, b] = q.front();
                q.pop();
                for(int j = 0; j < 4; j++)
                {
                    int x = a + dx[j], y = b + dy[j];
                    if(x >= 0 && x < m && y >= 0 && y < n && maze[x][y] == '.' && !vis[x][y])
                    {
                        // 判断是否已经到达出口
                        if(x == 0 || x == m - 1 || y == 0 || y == n - 1)
                            return step;
                        q.push({x, y});
                        vis[x][y] = true;
                    }
                }
            }
        }

        return -1;
    }
};